The present invention relates to a method of controlling a power assisted steering apparatus for a vehicle.
Various methods are known for controlling a power assisted steering apparatus for a vehicle. One known method is described in U.S. Pat. No. 5,198,981. The method analyzes vehicle condition signals during a steering maneuver to determine a steering torque command. The steering torque command represents the desired steering effort by the operator of the vehicle during the steering maneuver. The method also employs a torque sensor to measure a column torque actually applied by the operator. The column torque is preferably determined by measuring the torque across a torsion bar. The method compares the column torque to the steering torque demand to produce an error signal. The error signal is used to control an electric power assisted steering apparatus.
The method disclosed in U.S. Pat. No. 5,198,981 fails to consider the torque required to overcome the inertia of the hand wheel. This torque is felt by the operator and affects the overall steering effort exerted by the operator. A method for controlling a steering apparatus that accounts for the torque necessary to overcome hand wheel inertia is desirable.
The present invention is a method for controlling a steering apparatus of a vehicle. At least one signal indicative of a condition of the vehicle during a steering maneuver is provided to a controller. The vehicle condition signal is analyzed to determine a desired operator torque to be applied to a hand wheel of the vehicle. Inertia of the hand wheel of the vehicle is determined. An acceleration of the hand wheel is determined. A hand wheel torque is calculated by multiplying the inertia of the hand wheel with the acceleration of the hand wheel. A column torque across a torsion bar is determined. An error signal is produced by subtracting the hand wheel torque and the column torque from the desired operator torque. The steering apparatus is controlled with the error signal.